Planck–Einstein relation

The Planck–Einstein relation[1][2][3] is also referred to as the Einstein relation,[1][4][5]Planck's energy–frequency relation,[6] the Planck relation,[7] and the Planck equation.[8] Also the eponym Planck formula[9] belongs on this list, but also often refers to Planck's law instead.[10][11] These various eponyms are far from standard; they are used only sporadically, neither regularly nor very widely. They refer to a formula integral to quantum mechanics, which states that the energy of a photon, E, known as photon energy, is proportional to its frequency, ν:

The de Broglie relation,[5][12][13] also known as the de Broglie's momentum–wavelength relation,[6] generalizes the Planck relation to matter waves. Louis de Broglie argued that if particles had a wave nature, the relation E = hν would also apply to them, and postulated that particles would have a wavelength equal to λ = h/p. Combining de Broglie's postulate with the Planck–Einstein relation leads to